The present invention relates to a vacuum deposition apparatus capable of depositing a thin film composed of constant composition, from components which have different vapor pressures at a constant temperature, for manufacturing uniform products, and particularly to a substrate-heating device, and boat structure, for a vacuum depositing apparatus. The substrate-heating device is provided with a plurality of heating blocks with predetermined-distance intervals respectively between them, in conjunction with the form of the substrate holder, so as to decrease temperature differences among various portions of the substrate at the time of heating. The temperature of each heating block is separately and independently controlled so that, even if the temperature differences occur on the substrate at the time of heating the substrate, input to the respective blocks is changed thereby easily evening-out the temperature of the substrate. The boats for containing the material, which is to be evaporated or sublimated and deposited on the substrate, are mounted at the bottoms thereof, in sliding clamp-type mounting devices for counterbalancing thermal expansion of the boats themselves, so as to extend the useful lives of the boats.
Usually, for example, in a case when a compound semiconductor material which is composed of constituents which are different in vapor pressure from one another at a working temperature, such as indium antimonite, InSb, the temperature and pressure within the interior of the depositing chamber are important operating parameters. When the pressure is constantly maintained within a vacuum in a depositing chamber, the antimony, Sb, of the compound indium antimonite, InSb, can be instantly unintentionally re-evaporated due to temperature differences within the interior of the depositing chamber, so that the film that is vacuum-deposited on the surface of the substrate mounted on the substrate holder is not uniformly composed.
Consequently, the greater the temperature difference among various regions of the substrate is, the more anisotropic is the deposited film. Therefore, it is desirable to reduce as much as possible the temperature differences among various regions of substrates existing at the time of heating. Conventionally, as devices for heating the substrate in vapor-depositing apparatus, there has been mainly used halogen lamps as shown at 31 in FIG. 6A, and also there has been conventionally practiced a method for heating a plurality of substrate regions by simultaneously using halogen lamps 31 and C-G heaters 32, as shown in FIG. 6B.
However, in former case, not only is the difference of heating great according to the angle at which light radiated from the halogen lamp 31 is directly irradiated onto the substrate mounted on the substrate holder 33, but also, heat loss caused by heat dispersion within the interior of chamber, which is substantially larger than the substrate 34 requires increased heating, whereby temperature differences among portions of the substrate 34 are great. If a thermocouple 35 is used for detecting the temperature within the interior of chamber and it is disposed at a predetermined location for compensating for differences in the temperature of the substrate, a standard temperature setting is difficult, and, even if a standard temperature is set, temperature differences are great. Therefore, there has remained a problem in temperature control of the substrate.
In the case of simultaneously using both a halogen lamp 31 and a C-G heater 32, and the C-G heater 32 is provided at immediately above the substrate 33 for directly heating the substrate, since a heat-dispersing device capable of uniformly distributing the heat radiated from the C-G heater 32 is not present, heat differences between the portion immediately below the heater and the portion between the two heaters is great. Therefore, even if the substrate is substantially heated, temperature differences among respective portions of the substrate have occurred.
When a semiconductor film is deposited under the above-described uneven heating conditions, since the temperature differences among respective portions of the substrate are great, many instances of anisotropic characteristics in the deposited films have occurred.
Further, since the boat from which the film-forming material is evaporated is connected directly to the power-feeding electrodes, heat-expansion of the boat cannot be counterbalanced in case of a prior art ceramic boat (BN or Al.sub.2 O.sub.3). Accordingly, the boat can be bent or cracked. Consequently, uniform heating of an entire boat has been difficult.